How do I merge the body and the legs?
I would try this:
Select your leg on Object mode, change to Edit mode
press &quot;A&quot; to select the whole leg
copy with ctrl+c
unselect clicking everywhere else
turn into object mode again
hide the leg you've just selected before with &quot;H&quot; and select the torso on object mode
change to edit mode and PASTE THE LEG (CTRL+V)
If I'm right, now you have a leg into the vertices group of the torso and now you can link them!